In the past, various types of electrical switches were utilized in association with prime movers, such as a split phase electric motor for instance, so as to render a start winding in a winding circuit of the electric motor generally ineffective at a predetermined speed of the electric motor upon energization thereof. In other words, both the start winding and a run winding of the winding circuit were initially excited upon energization of the electric motor so as to bring a rotatable assembly thereof up to the predetermined speed, and a speed responsive system associated with the rotatable assembly was actuated generally at the predetermined speed to effect the switching operation of the electrical switch. Upon this switching operation, the start winding was rendered ineffective in the winding circuit, and only the run winding remained effectively magnetically coupled with the rotatable assembly so as to operate the electric motor at its synchronous speed. One type of these past electrical switches is shown in U.S. Pat. No. 3,313,905 issued Apr. 11, 1967 to W. S. Zagorski.
Of course, these past electrical switches employed several different switching arrangements. For instance, in some of the past electrical switches a single pole double throw switch was connected in circuit relation with the run and start winding of the motor winding circuit and across a power source. In others of the past electrical switches, a pair of single pole single throw switches were respectively connected in circuit relation with the run and start windings of the motor winding circuit and across the power source. Of course, other types of switching arrangements may also have been employed to control the motor winding circuit. In any event, various types of plungers were reciprocally movable in these past electrical switches to effect the switching operation of the switches between their circuit controlling positions so as to selectively control the excitation of the run and start windings of the motor winding circuit, and as previously mentioned, the plunger of the past electrical switches were driven by the speed responsive system of the electrical motor.
Another type of the past electrical switches utilized in association with an electric motor is disclosed in U.S. Pat. No. 3,381,197 issued Apr. 30, 1968 to J. L. Waters et al. In addition to performing the switching operation to render the start winding of the motor winding circuit ineffective at the predetermined speed of the electric motor, as discussed hereinabove, this other type of past electrical switch was also operative to control an auxiliary circuit electrically disassociated from the motor winding circuit and externally thereof. In one particular application, this other type of past electrical switch was utilized on a split phase electric motor for driving or operating an electric clothes dryer. For instance, the electric motor was drivingly associated with the clothes tumbler of the electric dryer, and an electrically energized heating element of the electric clothes dryer was connected in the auxiliary circuit through the other type past electrical switch across the power source. In other words, the electrical switch contained one switching arrangement connected in circuit relation between the motor winding circuit and the power source and another switching arrangement connected in the auxiliary circuit between one side of the heating element for the clothes dryer and one side of the power source. Therefore, when the electric motor was selectively deenergized by the operator turning off the clothes dryer, the plunger of the electrical switch was moved by the speed responsive system of the electric motor to operate the switching arrangement controlling the motor winding circuit so as to deenergize it and also to operate the switching arrangement in the auxiliary circuit to an open circuit position thereby to effect deenergization of the heating element of the clothes dryer.
At least one of the disadvantages or undesirable features of the past electrical switches controlling both the winding circuit and the auxiliary circuit, as discussed above, is believed to be that if somehow the heating element of the clothes dryer became grounded, power could be delivered thereto through the auxiliary circuit from one side of the power source even though the switching arrangement of the past electrical switch was actuated to its open position in the auxiliary circuit between the other side of the power source and the heating element. Of course, if this grounding of the heating element did, in fact, occur, the delivery of power thereto when the clothes dryer and electric motor were deenergized, as discussed above, may effect the continued energization of the heating element which could cause a fire. Further, it is also possible that the metallic housing or cabinet of such electric clothes dryers, or a part thereof, may be deleteriously energized by the grounding of the heating element in the manner suggested above which may, of course, result in the electrical shocking of anyone who may touch such deleteriously energized housing.